1. Field of the Invention
The present invention relates to a current drive circuit, and in particular, to a current drive circuit of a current mode bus interface system and a method of boosting a current using the same.
2. Description of the Related Art
Typically, to transmit/receive signals between integrated circuits, either a voltage mode transmitting/receiving operation or a current mode transmitting/receiving operation is performed.
The voltage mode transmitting/receiving operation has a resistive-capacitive delay, and the current mode transmitting/receiving operation has been studied to improve the voltage mode transmitting/receiving operation.
The current mode transmitting/receiving operation observes a current of a transmitted/received signal. The current mode transmitting/receiving operation maintains a voltage level of a transfer line at a predetermined level, and transfers data by changing a level of a current flowing through the transfer line.
A transmitter may sequentially transfer digital data using two logic levels ‘1’ and ‘0’. For example, a current level of about 17 mA through 23 mA may be set to logic level ‘1’, and the current level of about 0 mA through 6 mA may be set to logic level ‘0’. At this time, a receiver may recover the transmitted digital data by determining the current level of the transmitted signals.
The current mode transmitting/receiving operation may reduce the resistive-capacitive delay since the voltage level is maintained at the predetermined level.
In the current mode transmitting/receiving operation, the transmitter may transmit a reference current with a data current. For example, the transmitter sets the current level of about 17 mA through 23 mA to logic level ‘1’, sets the current level of about 0 mA through 6 mA to logic level ‘0’, and transmits the data current based on the logic levels. At the same time, the transmitter transmits the reference current of about 10 mA.
The receiver receives both the data current and the reference current to compare a magnitude of the data current with that of the reference current, and then, determines the logic level of the transmitted data current. For example, the receiver determines the transmitted digital data as logic level ‘1’ when the magnitude of the data current is larger than that of the reference current, and determines the transmitted digital data as logic level ‘0’ when the magnitude of the data current is smaller than that of the reference current.
As described above, the current mode transmitting/receiving operation that transmits/receives both the data current and the reference current is called a ‘pseudo-differential current mode’ transmitting/receiving operation.
It is desired that the mobile applications efficiently use charged electric energy to prolong an operation time of the mobile applications. One among various methods of reducing the power consumption helps parts to enter into a suspend mode based on a state of the applications.
In the case of a mobile application device such as a mobile phone, the parts for operations of corresponding applications consume the electric power during a normal operation mode. However, other parts are deactivated so the other parts no longer consume the electric power, except for a part for performing a mode transition during the suspend mode.
It is preferred that an operating current used for transmission/reception of the current mode bus interface system has a small magnitude. Additionally, according to an application, a capacitance component of a printed circuit board (PCB) used for transmission/reception of the current mode bus interface system may be increased.
Consequently, in the mode transition of the bus interface system, when the mode transition is performed with the operating current, a time period required for performing the mode transition may be delayed.